--- a/png2ico.cpp.orig	2002-12-07 14:37:58.000000000 -0800
+++ b/png2ico.cpp	2019-12-19 17:04:47.861832968 -0800
@@ -35,6 +35,7 @@ Notes about transparent and inverted pix
 #include <cstdio>
 #include <vector>
 #include <climits>
+#include <cstring>
 
 #if __GNUC__ > 2
 #include <ext/hash_map>
